Yamaha YBR 125 Custom - Rev Counter Issue

[member1351]

Hi All,

I am new to this forum and sorry for starting with a technical question as my first post!

My bike: Yamaha YBR 125 Custom 2010

I bought the bike a couple of weeks ago and loving it. It rides and look great. And work as it should apart from its tachometer not working at all. The previous owner stated that it stopped working halfway through a journey for him a while back and he never bothered looking into it.

II am trying to fix it, so opened the instrument cluster and checked everything, all the wiring look fine and I get a reading of 26.7v AC (increases to 27v AC when I rev it up) on the Blue/Yellow wire (which I believe comes straight from the ECU) and then 12v DC on the Brown cable. The Ground seems to be fine too.

I thought that it might be the tachometer unit itself so I ordered a second hand one from eBay (came from a 2013 model). But no luck when connected the replacement unit too.

I am really puzzled - the likelihood of the replacement tachometer being faulty must be very very low. So what can the issue be?

The battery seems to be new.

The battery connections are solid and spotless like new.

The bike runs and sounds as it should.

Can anyone help please?

Any idea?

Really appreciate your help.

Many thanks.

[member1351]

Hello,

I was hoping that someone out there could help, please?

Yamaha YBR 125 owners?

Anyone experienced a similar issue?

Thank you.

[ThePhatomfart]

Hi , dont know this bike , but would ave thought 20+volts coming from the ECU to the clocks seem a lot, the pulse for the Tach would come from somewhere like the CKP to produce that pulse to the ECU, as the bike is running the CKP must be working OK, but maybe just a clean of it may work

[dynax]

You may find some answers on Youtube, sorry that no seems to be able to help, it's not something i have experienced either, good luck with getting it fixed or replaced if it can't be repaired

[member1351]

Hi , dont know this bike , but would ave thought 20+volts coming from the ECU to the clocks seem a lot, the pulse for the Tach would come from somewhere like the CKP to produce that pulse to the ECU, as the bike is running the CKP must be working OK, but maybe just a clean of it may work

 

Hello mate,

I will have a look at the CPK.

Since my last post, I hardwired the Tach directly onto the Ignition Coil and bang the Tach started working. However I don't believe the RPM readings are accurate or even realistic when feeding directly from the Ignition Coil.

Maybe it should feed it directly from CPK?

Could the ECU unit be at fault here?

I suppose the readings go to ECU and that is where it gets put into a correct range!?

Can the Rectifier be at fault here?

Thanks.

[ThePhatomfart]

I tend to think it's the ECU , and with the absence of a Speed sensor could be the CKP thats supplying the pulse, there are some ECU's on Ebay £50, but would be better if you knew someone that you could borrow their's to find out, as the bikes running fine the CKP is working

[member1351]

Yes, I am thinking ECU as well - some cheaper ones can be found on eBay around £30ish. I am tempted.

Not sure if there is anyone around me in Berkshire that I can borrow the ECU unit from - especially with the current chaos!

I will test the CKP as well. It didn't occur to me that CKP could also play a part here!

[member1351]

One thing I certainly need is a reference as to what the RPM readings should be for this bike.

For example in normal riding condition what should be the reading in 1st, 2nd, 3rd ... gears.

I feel that the RPM readings I am getting when I wire it directly to the Ignition Coil are far too low.

At around 30mph, it is hardly reaching 2500rpm while I can hear the engine high in REV. That doesn't sound right to me!

[ThePhatomfart]

Take a look at this although 2007 should be in the same ball park

https://yamahaclub.com/forums/topic/9005-ybr125-2007-wiring-diagram-and-technical-really-technical-spec/

Idle 1400 rpm

[member1351]

Thanks for this.

Very interesting. The Tach doesn't even want to move when in Idle. It only moves when it is rev'd up.

[member1351]

Hi ThePhatomfart,

I tested the CKP as well. Looks intact and return the recommended resistance result as per Haynes manual.

I also re-tested the continuity from Tach to ECU - absolutely fine. So must be the ECU!

Unless someone else out here might have a different view!

[member1351]

Update:

The issue has now been fixed!

Replaced the ECU unit with a pre-owned one (ordered from eBay) and the tachometer is now working again.

[ThePhatomfart]

Update:

The issue has now been fixed!

Replaced the ECU unit with a pre-owned one (ordered from eBay) and the tachometer is now working again.

 

Glad your sorted